To start, get into a lunge position with your right knee up and your left knee on the floor. Rest your hands on the ground, directly underneath your shoulders. Next, flex your raised right knee outward, so that you’re resting on the outside of your right foot. Press your chest forward to increase the stretch. Hold this pose for 10 seconds, then repeat on the other side of your body.

To achieve this stretch, start out on your hands and knees. Slowly widen your knees out as far as they can go, and make sure to keep your lower legs in line with your knees. Your lower legs and feet should be parallel with one another. Next, ease your upper body forward on your forearms and reach forward until you feel the stretch. Hold this pose for about 10 seconds.

Grade III (severe): A complete tear in your muscle that causes severe pain and swelling and you can't bear weight on that leg, making it difficult to walk. You've also lost more than 50 percent of your muscle function. These injuries are less common and may need surgery to repair the torn muscle. They can take several months or more to completely heal.
You can roll on just about anything. I've used several different types of foam rollers, a Rumble Roller, lacrosse balls, PVC pipe, a number of weird stick-shaped things. I've also been getting great results using the Body Wrench, an awesome device that is basically a combination of all of the above. I have found that different materials are suitable for different areas on different bodies, so feel free to experiment and find what works best for you.

Then, consider that where there is tightness there might also be weakness somewhere near by. With 11 muscles contributing to the gross movement of hip flexion, it’s possible that some of the muscles are stronger than others. If some are stronger and work harder than others they might get overly tight. Identifying which hip flexors are weak and strengthening them is another way to approach hip flexor tightness.

To complete this stretch, get into the same kneeling position from the half kneeling hip flexor stretch. Whichever leg you have raised, place that hand on your hip. (So, if you’re doing this exercise with your right leg, place your right hand on your right hip, and vice versa.) Next, tighten your glute muscles, and reach around your body with your free hand to grab that foot. Pull that foot upwards towards your upper body
Of course, you know what it feels like to have a tight muscle. But tight hips aren't just uncomfortable—they can lead to all sorts of other aches and pains, especially in the lower back. "People focus on the hips and say their hips are tight, but we don't always think about the fact that the lower back connects to our legs at the hip," Charlee Atkins, C.S.C.S., instructor at Soul Annex in New York City and creator of Le Stretch class, tells SELF. Tight hip flexors make it harder for your pelvis to rotate properly, which can cause your lower back to overcompensate, "and this can be a setup for lower-back injury," Teo Mendez, M.D., an orthopedic surgeon at NY Orthopedics who focuses on operative and non-operative management of sports-related injuries, musculoskeletal injuries, and arthritis, tells SELF.